Saturday, 24 September 2016

Do placebos work if you don't believe in them?

Yesterday I watched the glucosamine trial on BBC's Trust Me, I'm a Doctor (which I saw on iPlayer) with interest as I am currently taking glucosamine for a bit of joint pain in my knees.

The detailed trial results are here, but the essence is that 50% of the trial group did a simple strengthening exercise (with 80% success rate), the other half of the trial took a supplement (with 55% success rate).

55% is still pretty good, but at the end of the trial it was revealed that the supplement was in fact a sugar pill - a placebo. They weren't taking glucosamine at all.

So I then wondered about the supplement half of the trial. Did their joint pain immediately come back, now that they knew that they had been taking a placebo? Or did it stay away?

The programme didn't answer that, but a quick Google search revealed this article in the Guardian, which talks about research that placebos seem to work even when patients know they're taking a placebo.

(I also found this article criticising the study on the grounds that because the subjects were told that placebos have a powerful effect, they were lied to and effectively manipulated into believing that they would - and as a result the placebo effect kicked in.)

Which makes me wonder what's going on. It seems clear to me that there's something psychological going on, but is a case of "This nice man in a position of authority is telling me that this sugar pill works, therefore it will."? Or maybe "Because I am doing something about my pain I am therefore getting better."

Or is it something else?

One thing I haven't seen is whether placebos work if you don't believe in them. So for that 45% of the trial, why didn't it work for them? Was it because the pain was too intense, or was there something else going on?

(As for me, I'm trying the exercises as I'd rather not take a supplement if I don't need to. We'll see how that goes.)